Risk and Hazard Assessment for Projects Involving the Geological Sequestration of CO2

Publisher Summary Hazards due to geological sequestration are either caused by, or will lead to, a leakage of the sequestered CO 2 or both. They include acute hazards and diffuse hazards. As a result, CO 2 concentrations in the different environmental media exceed their normal ranges, resulting in various risks. A sudden release of CO 2 due to well cap failure or through fracture zones, although unlikely, could be the most hazardous event. A risk and consequence assessment methodology for carbon sequestration projects has been developed in this chapter, using a typical injection field as the source of hazard and leaking CO2 concentrations and fluxes as the key measures of risk and consequence to humans, animals, biota, property, agriculture, and water resources. Methods have been presented for quantifying the leakage rates via different pathways into various media, the resulting CO 2 concentrations, consequences, and risks. Results indicate that an acute, accidental release of CO 2 at the wellhead is the primary hazard, followed by leakage through a failed cap rock. Risks are the highest near the wellhead and dissipate radially away from the injection field. A better understanding of the associated uncertainty is needed to improve the confidence in risk projections, for which the methods presented provide a basis.